Caffeoyl Triterpenoid Esters as Potential Anti-ischemic Stroke Agents from Celastrus orbiculatus

In vitro and in silico analysis of Solanum torvum fruit and methyl caffeate interaction with cholinesterases

Oxidative stress along with dysfunction in cholinergic neurotransmission primarily underlies cognitive impairment. A significant approach to mitigate cognitive dysfunction involves the inhibition of cholinesterases, namely acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Exploring the potential antioxidant and anticholinesterase effects of edible plants holds promise for their utilization as botanicals to enhance cognition. Solanum torvum fruit with vast biological properties are used as food. In the present study, butanolic extract of S. torvum fruits (BESTF) was prepared. Additionally, the study investigated into the properties of methyl caffeate (MC), a compound present in S. torvum, obtained in its pure form. In vitro antioxidant and anticholinesterases activity of BESTF and MC were determined. BESTF and MC showed potent antioxidant property. BESTF and MC dose-dependently inhibited AChE (IC50 values: 166.6 µg/ml and 680.6 µM, respectively) and BChE (IC50 values: 161.55 µg/ml and 413 µM, respectively). BESTF and MC inhibited AChE and BChE in competitive mode. Active site gorge of AChE/BChE was occupied by MC which formed interaction with amino acids present in catalytic site and PAS in in silico. Further, molecular dynamics simulations followed by free energy calculation, principal component analysis and dynamic cross-correlation matrix provided the compelling evidence that that MC maintained stable interactions during MD simulation with AChE and BChE. Collectively, the results from the present study underlines the cognitive-enhancing effect of BESTF and MC.

Betulinic acid, a major therapeutic triterpene of Celastrus orbiculatus Thunb., acts as a chemosensitizer of gemcitabine by promoting Chk1 degradation

ETHNOPHARMACOLOGICAL RELEVANCE

Celastrus orbiculatus Thunb., also called as oriental bittersweet vine or climbing spindle berry, a traditional Chinese herbal medicine has been used to treat a spectrum of painful and inflammatory diseases for centuries. Explored for their unique medicinal properties, C.orbiculatus offers additional therapeutic effects on cancerous diseases. The effect of single-agent gemcitabine on survival has not long been encouraging, combination therapies provide patients multiple chances of benefit for improved clinical response.

AIMS OF THIS STUDY

This study aims at expounding the chemopotentiating effects and underlying mechanisms of betulinic acid, a primary therapeutic triterpene of C. orbiculatus in combination with gemcitabine chemotherapy.

MATERIALS AND METHODS

The preparation of betulinic acid was optimized using ultrasonic-assisted extraction method. Gemcitabine-resistant cell model was established by induction of the cytidine deaminase. MTT, colony formation, EdU incorporation and Annexin V/PI staining assays were used to evaluate cytotoxicity, cell proliferation and apoptosis in BxPC-3 pancreatic cancer cell line and H1299 non-small cell lung carcinoma cell line. Comet assay, metaphase chromosome spread and γH2AX immunostaining were applied for DNA damage assessment. Western blot and co-immunoprecipitation was used to detect the phosphorylation and ubiquitination of Chk1. Mode of action of gemcitabine in combination with betulinic acid was further captured in BxPC-3-derived mouse xenograft model.

RESULTS

We noticed that the extraction method had an impact on the thermal stability of C. orbiculatus. Ultrasound-assisted extraction at room temperature in shorter processing time could maximize the overall yields and biological activities of C. orbiculatus. The major constituent was identified as betulinic acid, and the pentacyclic triterpene represented the prominent anticancer activity of C. orbiculatus. Forced expression of cytidine deaminase conferred acquired resistance to gemcitabine, while betulinic acid displayed equivalent cytotoxicity toward gemcitabine-resistant and sensitive cells. A combination therapy of gemcitabine with betulinic acid produced synergistic pharmacologic interaction on cell viability, apoptosis and DNA double-strand breaks. Moreover, betulinic acid abrogated gemcitabine-triggered Chk1 activation by destabilizing Chk1 loading via proteasomal degradation. The combination of gemcitabine and betulinic acid significantly retarded BxPC-3 tumor growth in vivo compared to single-agent gemcitabine treatment alone, accompanied with reduced Chk1 expression.

CONCLUSIONS

These data provide evidence that betulinic acid is a potential candidate for chemosensitization as a naturally occurring Chk1 inhibitor and warrants further preclinical evaluation.

Structures and neuroprotective activities of triterpenoids from Cynomorium coccineum subsp. songaricum (Rupr.) J. Leonard

Cynomorium coccineum subsp. songaricum (Rupr.) J. Leonard has been widely used as a Chinese herbal remedy or a functional food for treating symptoms of aging or neurodegenerative diseases. A further investigation on the finding of active constituents led to the isolation and identification of four previously undescribed triterpenoids, together with 20 known compounds. Their structures were elucidated by extensive spectroscopic analysis (IR, NMR, HRMS, and CD). Sixteen compounds showed significant neuroprotective effects against glutamate-induced or oxygen-glucose deprivation-induced SK-N-SH cell death. Our findings revealed the active constituents of C. coccineum subsp. songaricum and indicated that both oleanane-type and ursane-type triterpenes could be valuable platforms for neurodegenerative agents based on primary structure-activity relationship analysis.

PDPOB Exerts Multiaspect Anti-Ischemic Effects Associated with the Regulation of PI3K/AKT and MAPK Signaling Pathways

The discovery of new therapeutic agents for ischemic stroke remains an urgent need. Here, we identified a novel phenyl carboxylic acid derivative, n-pentyl 4-(3,4-dihydroxyphenyl)-4-oxobutanoate (PDPOB), with anti-ischemic activities. The in vitro anti-ischemic neuroprotective and anti-inflammatory capacities of PDPOB were investigated using neuronal cells suffering from oxygen-glucose deprivation/reperfusion (OGD/R) and microglial cells stimulated by lipopolysaccharide (LPS). PDPOB attenuated the OGD/R-evoked cellular damage of SH-SY5Y cells and primary cortical neurons in a concentration-dependent manner. Likewise, PDPOB displayed protective roles against OGD/R-evoked multiaspect neuronal deterioration in SH-SY5Y cells, as evidenced by alleviated mitochondrial dysfunction, oxidative stress, and apoptosis. A further study unveiled the accelerated phosphorylation of protein kinase B (AKT) by PDPOB treatment, while blockade of phosphoinositide 3-kinase (PI3K)/AKT signaling substantially diminished the neuroprotective capacities of PDPOB. Additionally, the PDPOB pretreatment dampened the LPS-evoked neuroinflammation in BV2 cells, characterized by the suppressed secretion of nitric oxide (NO) and proinflammatory cytokines, as well as normalized expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Western blotting further revealed that PDPOB abated the overabundant phosphorylation of the extracellular signal-regulated kinase (ERK), c-Jun-N-terminal kinase (JNK), and p38 in LPS-exposed BV2 cells. The intravenous application of PDPOB (30 mg/kg, single dose) attenuated ipsilateral cerebral infarction in middle cerebral artery occlusion (MCAO) rats, accompanied by recovered neurological behaviors. Collectively, the above observations provided substantial evidence for the favorable properties and mechanistic explanations of PDPOB in the regulation of ischemia-associated neuronal injury and microglial inflammation, which may furnish ideas for the discovery of new therapeutic strategies against cerebral ischemia.

Protective effects of natural compounds against oxidative stress in ischemic diseases and cancers via activating the Nrf2 signaling pathway: A mini review

Oxidative stress, an imbalance between reactive oxygen species and antioxidants, has been seen in the pathological states of many disorders such as ischemic diseases and cancers. Many natural compounds (NCs) have long been recognized to ameliorate oxidative stress due to their inherent antioxidant activities. The modulation of oxidative stress by NCs via activating the Nrf2 signaling pathway is summarized in the review. Three NCs, ursolic acid, betulinic acid, and curcumin, and the mechanisms of their cytoprotective effects are investigated in myocardial ischemia, cerebral ischemia, skin cancer, and prostate cancer. To promote the therapeutic performance of NCs with poor water solubility, the formulation approach, such as the nano drug delivery system, is elaborated as well in this review.

Triterpenoids from Celastrus orbiculatus Thunb. inhibit RANKL-induced osteoclast formation and bone resorption via c-Fos signaling

Fourteen triterpenes, lup-20(29)-ene-3β,6β-diol (1), betulin (2), lupeol caffeate (3), 3β-caffeoyloxylup-20(29)-en-6α-ol (4), betulin-3β-yl-caffeate (5), 3β-trans-feruloylbetulin (6), betulinaldehyde 3-caffeate (7), 3-O-trans-caffeoylbetulinic acid (8), dammarenediol II 3-caffeate (9), 12-oleanene-3β,6α-diol (10), 11α-hydroxy-3β-amyrin (11), nivadiol (12), 29-hydroxyfriedelin (13), and celastrusin A (14) were isolated from Celastrus orbiculatus Thunb. and evaluated for their activity on receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation in bone marrow macrophages (BMMs). Compounds betulin (2), betulin-3β-yl-caffeate (5), 3β-trans-feruloylbetulin (6), and 3-O-trans-caffeoylbetulinic acid (8) significantly inhibited osteoclast formation in a dose-dependent manner. Among these, betulin-3β-yl-caffeate (5) exhibited the most potent inhibitory activity. We demonstrated that betulin-3β-yl-caffeate (5) suppressed F-actin-ring formation and bone resorption activity. At the molecular level, betulin-3β-yl-caffeate (5) inhibited RANK-induced expression of c-Fos and the induction of nuclear factor of activated T cells 1 (NFATc1), a key transcription factor for osteoclast formation, and it also downregulated mRNA expression of osteogenesis-associated marker genes including tartrate-resistant acid phosphatase (TRAP), dendritic cell-specific transmembrane protein (DC-STAMP), and matrix metalloprotein (MMP). These results indicate that betulin-3β-yl-caffeate (5) may be a promising candidate for the treatment of osteoclast-related diseases such as osteoporosis.

Traditional uses, secondary metabolites, and pharmacology of Celastrus species - a review

ETHNOPHARMACOLOGICAL RELEVANCE

Plants of genus Celastrus (Celastraceae) have been widely used in traditional Chinese medicine (TCM) and Indian medicine to treat cognitive dysfunction, epilepsy, insomnia, rheumatism, gout, and dyspepsia for thousands of years.

AIM OF STUDY

We critically summarized the current evidence on the botanic characterization and distribution, ethnopharmacology, secondary metabolites, pharmacological activities, qualitative and quantitative analysis, and toxicology of Celastrus species to provide perspectives for developing more attractive pharmaceuticals of plant origin.

MATERIALS AND METHODS

The relevant information on Celastrus species was gathered from worldwide accepted scientific databases via electronic search (Web of Science, SciFinder, PubMed, Elsevier, SpringerLink, Wiley Online, China Knowledge Resource Integrated, and Google Scholar). Information was also obtained from the literature and books as well as PhD and MSc dissertations. Plant names were validated by "The Plant List" (www.theplantlist.org).

RESULTS

Comprehensive analysis of the above mentioned databases and other sources confirmed that ethnomedical uses of plants of Celastrus genus had been recorded in China, India, and other countries in Southern Asia. The phytochemical investigation revealed the presence of β-dihydroagarofuranoids, diterpenoids, triterpenoids, tetraterpenes, phenylpropanoids, alkaloids, flavonoids, lignans, and others. The crude extracts and isolated constituents have exhibited a wide range of in vitro and in vivo pharmacological effects, including antitumor, cytotoxic, insecticidal, antimicrobial, anti-rheumatoid arthritis (RA), anti-inflammatory, anti-ageing and antioxidative, and neuroprotective activities.

CONCLUSION

Plants of genus Celastrus have been confirmed to show a strong potential for therapeutic and health-maintaining effects, in light of their long traditional use and the phytochemical and pharmacological studies summarized here. Currently, pharmacological studies of this genus mainly focus on Celastrus paniculatus Willd. and Celastrus orbiculatus Thunb. Therefore, more pharmacological investigations should be implemented to support traditional uses of other medicinal plants of the genus Celastrus. Moreover, studies on the toxicity, bioavailability, and pharmacokinetics, in addition to clinical trials, are indispensable for assessing the safety and efficacy of the secondary metabolites or extracts obtained from plants belonging to this genus.

Cytotoxic abietane and kaurane diterpenoids from Celastrus orbiculatus

Celastrus orbiculatus is a medicinal plant belonging to the Celastraceae family. In this survey on the secondary metabolites of plants for obtaining antitumor substances, the chemical constituents of the stems of C. orbiculatus were investigated. Nortriptonoterpene (1), a new C₁₉-norabietane diterpenoid, together with six other known abietane-type diterpenoids (2-7) and five known kaurane-type diterpenoids (8-12) were isolated and identified from the EtOAc extract of C. orbiculatus. Their structures were elucidated on the basis of extensive spectroscopic methods, including UV, IR, HR-ESI-MS, ECD, and NMR experiments, and by comparison with literature data. Compound 1 is a new C₁₉-norabietane diterpenoid with 19 carbons. All compounds except for 10 and 11 were isolated from C. orbiculatus for the first time. The NMR data of 9 were reported for the first time. Compounds 1, 7 and 11 showed cytotoxicities against SGC-7901 with IC₅₀ values of 63.2, 80.9 and 56.7 μM, respectively.

Thevetiaflavone from Wikstroemia indica ameliorates PC12 cells injury induced by OGD/R via improving ROS‑mediated mitochondrial dysfunction

Cerebral ischemia and following reperfusion affects many people worldwide. To discover efficient therapeutic approaches, numerous natural products have been investigated. The current study investigated the protective effects of thevetiaflavone, a natural flavonoid obtained from Wikstroemia indica, and the associated mechanisms using PC12 cells induced by oxygen and glucose deprivation. As a result, thevetiaflavone improves cell viability and suppresses the leakage of lactate dehydrogenase from the cytoplasm. Further investigation of the mechanisms demonstrated that thevetiaflavone decreases overproduction of ROS and ameliorates ROS‑mediated mitochondrial dysfunction, including collapse of mitochondrial membrane potential and mitochondrial permeability transition pore opening. Thevetiaflavone reduces the intracellular Ca2+ level, which is closely associated with mitochondrial function and interplays with ROS. Furthermore, thevetiaflavone inhibits apoptosis in PC12 cells through upregulating the expression of Bcl‑2 and downregulating that of Bax and caspase‑3 in addition to increasing the activity of caspase‑3. These results further indicate the protective effects of thevetiaflavone in vivo and its application in the clinic.